Launch extension: allow `eventInfo` to be retrieved with data elements

### Expected Behaviour
Given an ACDL push like so:
```
window.adobeDataLayer.push({
"event": myEvent",
"eventInfo": { foo: "bar" }
});
```
Then there should be an ACDL data element type that when provided with the key `eventInfo.foo`, the data element returns `"bar"`.

The Data Layer Computed State data element type is not able to read `eventInfo`, because `eventInfo` does not persist in the data layer.

### Actual Behaviour
There is no such data element to retrieve `eventInfo` fields.

#### Steps to Reproduce
See "Expected Behaviour".

#### Platform and Version
All platforms, all versions.

#### Sample Code that illustrates the problem
See "Expected Behaviour".

Start by locating the Data Layer Computed State data element and the code that handles ACDL pushes, then inspect any nearby tests. Add or identify the data element entry point for eventInfo fields and verify that a key such as eventInfo.foo returns "bar" without relying on persisted data-layer state.

Written by the indexing model from the issue text.